The pregnancy of a 31-year-old infertility patient is described. After gamete intra-Fallopian transfer, her pregnancy evolved uneventfully until the 18th week of gestation, when vaginal bleeding occurred. Ultrasonographic findings suggested a molar pregnancy with two live fetuses. At 24 weeks gestation, two male infants were spontaneously delivered. Fetal (46 XY) and molar (46 XX) karyotypes and post-mortem findings were consistent with a bizygotic twin pregnancy associated with a complete hydatidiform mole. The pathogenesis and obstetrical management are discussed.